Control circuit of electrostatic capacitive sensor and electronic device using the same

ABSTRACT

An electrostatic capacitive sensor includes a plurality of transmitter electrodes, a plurality of receiver electrodes, and a control circuit. The control circuit includes: a transmitter circuit configured to apply a periodical transmission signal to each of the plurality of transmitter electrodes; and a receiver circuit configured to generate, based on a reception signal generated in each of the plurality of receiver electrodes in response to the transmission signal, a detection signal indicating a change in electrostatic capacitance formed at each of intersections of the plurality of transmitter electrodes and the plurality of receiver electrodes, wherein the transmitter circuit and the receiver circuit are configured to switch between a first mode and a second mode, in the first mode, the transmission/reception signal is sequentially applied/monitored and in the second mode, the plurality of transmitter/receiver electrodes are grouped so that the same signal is applied to the same group.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation-in-part of application Ser. No.13/839,844, filed Mar. 15, 2013, the entire contents of which areincorporated herein by reference; and is based upon and claims thebenefit of priority under 35 U.S.C. §119 to Japan Patent Application No.2012-62291, filed on Mar. 19, 2012, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a mutual capacitance type touch panel.

BACKGROUND

In recent years, electronic equipment such as computers, mobile phones,tablet PCs (personal computers), PDAs (personal digital assistants) andso on have become mainstream and now also include touch panels as inputdevices for manipulating the electronic equipment through the touch of afinger. Mutual capacitance type touch panels are developed for thesetypes of devices.

A mobile phone ceases to detect whether or not a touch panel is touchedwhen a user puts his/her ear to the mobile phone for calling. In thiscase, the contact of his/or her head to the touch panel of the mobilephone will not be detected as the action of touching the touch panel. Inaddition, when the user puts his/her ear to the mobile phone forcalling, a display of the mobile phone is turned off in order to savepower. Such type of a mobile phone has an optical proximity sensordisposed at a position corresponding to the head of the user whencalling. The proximity sensor includes a pair of a light emitting deviceand a light receiving device. The light receiving device detects lightemitted from the light emitting device and reflected by a detectiontarget such as a user's head.

However, the use of the optical proximity sensors increases the numberof components and production costs of the mobile phone. In addition, alight passage needs to be provided in the housing of the mobile phone,which restricts the design of the mobile phone.

SUMMARY

The present disclosure provides some embodiments of a mutual capacitancetype electrostatic capacitive sensor which can be also used as aproximity sensor.

According to one aspect of the present disclosure, there is provided acontrol circuit of an electrostatic capacitive sensor including aplurality of transmitter electrodes disposed in parallel in a firstdirection and a plurality of receiver electrodes disposed in parallel ina second direction and spaced apart from the plurality of transmitterelectrodes by specific intervals. The control circuit includes: atransmitter circuit configured to apply a periodical transmission signalto each of the plurality of transmitter electrodes; and a receivercircuit configured to generate, based on a reception signal generated ineach of the plurality of receiver electrodes in response to thetransmission signal, a detection signal indicating a change inelectrostatic capacitance formed at each of intersections of theplurality of transmitter electrodes and the plurality of receiverelectrodes. The transmitter circuit is configured to switch between afirst mode where the transmission signal is sequentially applied to theplurality of transmitter electrodes and a second mode where theplurality of transmitter electrodes is grouped and the same transmissionsignal is applied to a plurality of transmitter electrodes belonging tothe same group. The receiver circuit is configured to switch between afirst mode where the reception signal generated in each of the pluralityof receiver electrodes is sequentially monitored to generate thedetection signal for each of the receiver electrodes, and a second modewhere the plurality of receiver electrodes are grouped into one or moregroups and receiver electrodes belonging to the same group are connectedin common to generate the detection signal for each group.

In the second mode, the plurality of transmitter electrodes belonging tothe same group acts as a single electrode having a large area. As aresult, detection sensitivity of the change in capacitance can beincreased and accordingly it is possible to detect a condition where adetection target is in proximity to the panel and not directlycontacting to the panel.

In the second mode, the plurality of receiver electrodes belonging tothe same group acts as a single electrode having a large area. As aresult, detection sensitivity of the change in capacitance can beincreased and accordingly it is possible to detect a condition where adetection target is in proximity to the panel and not directlycontacting to the panel. Further, a combination of the mode of thereceiver circuit and the mode of the transmitter circuit can change thedetection sensitivity and the spatial resolution.

In some embodiments, the transmitter circuit may be set to the firstmode when the electrostatic capacitive sensor is operated as a touchpanel and may be set to the second mode when the electrostaticcapacitive sensor is operated as a proximity sensor.

In some embodiments, the transmitter circuit may be configured such thatthe number of groups can be changed in the second mode. In other words,the number of electrodes belonging to the same group may be changed.Thus, it is possible to change sensitivity and a spatial resolution inthe first direction which are in a trade-off relationship gradually.

In some embodiments, the control circuit may further include acontroller configured to control an operation mode of the transmittercircuit. The controller may switch between a first condition where thetransmitter circuit is fixedly set to the first mode and a secondcondition where the transmitter circuit is set to alternate between thefirst mode and the second mode in a time-divisional manner. Before theuser contacts the panel, both of proximity and touch can be monitored bysetting the transmitter circuit to the second condition. After the touchis detected, a touched coordinate can be detected with a spatialresolution by setting the transmitter circuit to the first condition.

In some embodiments, the receiver circuit may be configured such thatthe number of groups can be changed in the second mode. In other words,the number of electrodes belonging to the same group may be changed.Thus, it is possible to change sensitivity and a spatial resolution inthe second direction which are in a trade-off relationship gradually.

In some embodiments, the control circuit may further include acontroller configured to control operation modes of the transmittercircuit and the receiver circuit. The controller may switch between afirst condition where the transmitter circuit and the receiver circuitare fixedly set to the first mode and a second condition where thetransmitter circuit and the receiver circuit are set to alternatebetween the first mode and the second mode in a time-divisional manner.

According to another aspect of the present disclosure, there is provideda control circuit of an electrostatic capacitive sensor including: atransmitter circuit configured to apply a periodical transmission signalto each of a plurality of transmitter electrodes; and a receiver circuitconfigured to generate, based on a reception signal generated in each ofthe plurality of receiver electrodes in response to the transmissionsignal, a detection signal indicating a change in electrostaticcapacitance formed at each of intersections of the plurality oftransmitter electrodes and a plurality of receiver electrodes. Thereceiver circuit is configured to switch between a first mode where thereception signal generated in each of the plurality of receiverelectrodes is sequentially monitored to generate the detection signalfor each of the receiver electrodes and a second mode where theplurality of receiver electrodes are grouped into one or more groups andreceiver electrodes belonging to the same group is connected in commonto generate the detection signal for each group.

In the second mode, the plurality of receiver electrodes belonging tothe same group acts as a single electrode having a large area. As aresult, detection sensitivity of the change in capacitance can beincreased and accordingly it is possible to detect a condition where adetection target is in proximity to the panel and not directlycontacting to the panel.

In some embodiments, the receiver circuit may be set to the first modewhen the electrostatic capacitive sensor is operated as a touch paneland may be set to the second mode when the electrostatic capacitivesensor is operated as a proximity sensor.

In some embodiments, the receiver circuit may be configured such thatthe number of groups can be changed in the second mode.

In some embodiments, the control circuit may further include acontroller configured to control an operation mode of the receivercircuit. The controller may switch between a first condition where thereceiver circuit is fixedly set to the first mode and a second conditionwhere the receiver circuit is set to alternate between the first modeand the second mode in a time-divisional manner.

According to another aspect of the present disclosure, there is providedan electronic equipment including: a housing; a display panel disposedon one surface of the housing; an electrostatic capacitive sensordisposed at an overlapping portion of the housing with the displaypanel, the electrostatic capacitive sensor including a plurality oftransmitter electrodes disposed in parallel in a first direction and aplurality of receiver electrodes disposed in parallel in a seconddirection and spaced apart from the plurality of transmitter electrodesby specific intervals; the control circuit according to the aboveaspects, which is disposed within the housing and detects a change incapacitance of the electrostatic capacitive sensor; and a processorconfigured to receive a digital value corresponding to the detectionsignal generated by the receiver circuit of the control circuit anddetects a manipulation status of the electronic equipment by a userbased on the digital value.

In some embodiments, the electronic equipment may be a mobile terminaland the electronic equipment may further include a speaker disposed at aposition close to a user' ear when calling. The processor may refer tothe digital value obtained in the second mode and determine that theuser approaches the housing to the user′ head for calling if a change incapacitance formed by the transmitter and the receiver electrodesdisposed in the vicinity of the speaker increases. Accordingly, it ispossible to detect proximity of a user's head by using the electrostaticcapacitive sensor for use in a touch panel, without using an opticalproximity sensor.

In some embodiments, the processor may refer to the digital valueobtained in the second mode and determine that a user grips the housingif a change in capacitance of the transmitter and the receiverelectrodes disposed at one end of the housing to which the user′ thumbapproaches when the housing is gripped by the user and the transmitterand the receiver electrodes disposed at the other end of the housing towhich the other fingers approach increase.

Other aspects of the present disclosures may include any combinations ofthe above-described elements or conversion of expression of the presentdisclosure between methods, apparatuses and so on.

According to the aspects of the present disclosure, a mutual capacitancetype electrostatic capacitive sensor can be used as a proximity sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing a configuration of electronicequipment including a touch panel input device according to a firstembodiment.

FIG. 2 is a circuit diagram showing a configuration of the input devicehaving a control circuit according to the first embodiment.

FIGS. 3A and 3B are operation waveform diagrams of a transmitter circuitin a first mode and a second mode, respectively.

FIGS. 4A to 4C are operation waveform diagrams of a transmitter circuitwhere the number of groups is 1 to 3, respectively.

FIGS. 5A to 5C are circuit diagrams showing example configurations ofthe transmitter circuit of FIG. 2.

FIGS. 6A to 6C are views showing usage of an input device in each mode.

FIGS. 7A and 7B are operation waveform diagrams in first and secondconditions, respectively.

FIGS. 8A and 8B are circuit diagrams showing example configurations ofreceiver circuits of a control circuit according to a second embodiment.

FIG. 9 is a matrix table showing the mode combinations of a transmittercircuit and a receiver circuit based on the conditions set by thecontroller according to a third embodiment.

FIG. 10 is a perspective view showing a mobile terminal as one exampleof electronic equipment having a control circuit.

FIG. 11A is a view showing a side head proximity condition and FIG. 11Bis a view showing an output of a capacitive sensor unit under the sidehead proximity condition.

FIGS. 12A to 12C are views for explaining the side head proximitycondition.

FIGS. 13A to 13C are views for explaining a condition where a usertouches the vicinity of a calling speaker of a capacitive sensor unit.

FIG. 14A is a view showing a grip condition and FIG. 14B is a viewshowing an output of a capacitive sensor unit under the grip condition.

DETAILED DESCRIPTION

Embodiments of the present disclosure will now be described in detailwith reference to the drawings. Throughout the drawings, the same orsimilar elements, members and processes are denoted by the samereference numerals, and explanations of which will not be repeated. Theembodiments will be presented by way of example only, and are notintended to limit the scope of the disclosures. Indeed, all the featuresand configurations of the embodiments are not essential to the presentdisclosure.

Throughout the description, “a state where a member A and a member B iscoupled” may include not only a state where the member A and the memberB is physically directly connected but also a state where the member Aand the member B is indirectly coupled via another member, unless theanother member substantially affects the electrical connection statebetween the members A and B or damages main functions or effects of theconnection between the members A and B.

Similarly, “a state where a member C is provided between a member A anda member B” may include not only a state where the member C isphysically directly connected to the member A or the member B but also astate where the member C is indirectly connected to the member A or themember B via another member, unless the another member substantiallyaffects the electrical connection state between the members A and C orbetween the members B and C or damages main functions or effects of theconnection between the members A and C or between the member B and C.

First Embodiment

FIG. 1 is a circuit diagram showing a configuration of electronicequipment 1 including a touch panel input device 2 (simply referred toas an “input device 2”) according to a first embodiment. The inputdevice 2 is disposed on a surface of an LCD (liquid crystal display) 8,for example, and acts as a touch panel. The input device 2 determines Xand Y coordinates of a point touched by a user's finger, a pen or thelike (hereinafter representatively referred to as a “detection target6”).

The input device 2 includes an electrostatic capacitive sensor 4, acontrol circuit (capacitance detecting circuit) 100 and a processor 3.The electrostatic capacitive sensor 4 is a mutual capacitance type touchpanel in a matrix form. More specifically, the electrostatic capacitivesensor 4 includes M number of transmitter electrodes 10 _([1˜M]) (M isan integer of 2 or more) disposed in parallel in a first direction incolumns of the matrix and N number of receiver electrodes 12 _([1˜N]) (Nis an integer of 2 or more) disposed in parallel in a second directionin rows of the matrix. The allocation of the transmitter electrodes 10and the receiver electrodes 12 at the rows and the columns may be inreverse. The transmitter electrodes 10 and the receiver electrodes 12are arranged to be spaced apart from each other in the verticaldirection. The transmitter electrodes 10 and the receiver electrodes 12are capacitively coupled to each other at each of intersections of thetransmitter electrodes 10 and the receiver electrodes 12. Morespecifically, a pair of one transmitter electrode 10 and one receiverelectrode 12 forms a capacitive sensor unit 5 at the intersectionthereof. That is, the electrostatic capacitive sensor 4 includes aplurality of capacitive sensor units 5 arranged in a matrix form. Forconvenience of explanation, a capacitive sensor disposed at the i-th rowand the j-th column (i and j are integers) will be denoted by acapacitive sensor unit 5 _([i,j]). When an object such as a finger, apen or the like is touched to or approaches the capacitive sensor unit 5_([i,j]), a mutual capacitance C_(M[i,j]) of the capacitive sensor unit5 _([i,j]) is changed.

The control circuit 100 detects changes in mutual capacitances C_(M) ofthe capacitive sensor units 5 having different coordinates in thecapacitive sensor unit 4. More specifically, the control circuit 100cyclically and sequentially applies transmission signals to theplurality of transmitter electrodes 10 and selects a transmitterelectrode 10 on which a capacitance detection is to be performed. Then,the control circuit 100 detects a change in electrostatic capacitance ofthe capacitive sensor unit 5 formed between the selected transmitterelectrode 10 and each of the plurality of receiver electrodes 12. Theselected transmitter electrode 10 corresponds to a column coordinate anda receiver electrode 12 which has undergone a change in capacitancecorresponds to a row coordinate. Data representing the change incapacitance is transmitted to the processor 3. The processor 3determines a coordinate touched by a user based on the change incapacitance of each coordinate.

The electronic equipment 1 has been outlined in the above. Below, thecontrol circuit 100 according to the first embodiment will be nowdescribed in more details.

FIG. 2 is a circuit diagram showing a configuration of the input device2 having the control circuit 100 according to the first embodiment. Onlya portion relating to one transmitter electrode 10 _([i]) is shown inFIG. 2.

The transmitter electrode 10 _([i]) is capacitively coupled to aplurality of receiver electrodes 12 _([1]) to 12 _([N]) and formscapacitive sensor units 5 _([i, 1]) to 5 _([i,N]) having mutualcapacitances C_(M) with the receiver electrodes 12 _([1]) to 12 _(N),respectively. Reference symbol Rs denotes resistances of the transmitterelectrode 10 and the receiver electrodes 12, and reference symbol Csdenotes capacitances thereof. Though not shown in FIG. 2, the capacitivesensor units 5 may also be formed between other transmitter electrodes10 and the receiver electrodes 12 _([1]) to 12 _([N]) in a similarmanner as shown in FIG. 2.

The control circuit 100 includes a transmitter circuit 20, a receivercircuit 26 and a controller 50.

The control circuit 100 also has transmitter (TX) terminalsTX_([1 to M]) and receiver (RX) terminals RX_([1 to N]) formed for therespective receiver electrodes 12. TX terminal TX_([i]) of the controlcircuit 100 is connected to a corresponding transmitter electrode 10_([i]) and RX terminal RX_([j]) of the control circuit 100 is connectedto a corresponding receiver electrode 12 _([j]).

The transmitter circuit 20 generates a periodical transmission signal S1and applies it to the transmitter electrodes 10 _([1 to M]). Thetransmitter circuit 20 has a signal generator 22 and a driver 24provided for each transmitter electrode 10. The signal generator 22generates a periodical clock signal. The driver 24 receives this clocksignal and outputs a transmission signal S1 in synchronization with theclock signal to the transmitter electrode 10. The transmission signal S1is a periodical signal which alternates between a first voltage level(for example, a power source voltage V_(dd)) and a second voltage level(for example, a ground voltage V_(SS)).

When the electrostatic capacitive sensor 4 is used as a touch panel, thetransmitter circuit 20 selects (or scans) a plurality of transmitterelectrodes 10 _([1 to M]) in a time-divisional manner and applies thetransmission signal S1 to a selected transmitter electrode 10 while afixed voltage level (for example, the ground voltage V_(SS)) is appliedto the remaining transmitter electrodes 10.

The receiver circuit 26 generates, based on a reception signal I_(RX)generated in each of the plurality of receiver electrodes 12 _([1 to N])in response to the transmission signal S1, detection signals Vsindicating changes in mutual capacitances C_(M[1,1]) to C_(M[M,N]) of aplurality of capacitive sensor units 5 formed at intersections of theplurality of transmitter electrodes 10 _([1 to M]) and the plurality ofreceiver electrodes 12 _([1 to N]).

The receiver circuit 26 includes an integration circuit 30, a samplehold circuit 40, an amplifier 42 and an A/D converter 44. Some or allparts of the receiver circuit 26 may be provided for each of thereceiver electrodes 12. Some or all parts of the receiver circuit 26 maybe provided every several receiver electrodes 12 and shared by theseveral receiver electrodes 12 in a time-divisional manner.

An integration circuit 30 allocated to a j-th receiver electrode 12_([j]) detects changes in mutual capacitances C_(M[1,j]) to C_(M[M,j])of the capacitive sensor units 5 _([1,j]) to 5 _([M,j]) formed by thereceiver electrode 12 _([j]) and generates a detection signal Vs havinga level according to the changes in capacitances based on a receptionsignal I_(RX[j]). Specifically, the reception signal I_(RX) is a currentsignal and the detection single Vs is a voltage signal, and theintegration circuit 30 integrates the current I_(RX) and generates thedetection voltage Vs according to the changes in capacitances. Theintegration circuit 30 may employ a well-known circuit or a circuitwhich will be described later, without being particularly limited in itsconfiguration and type.

The sample hold circuit 40 samples and holds the detection voltage Vsgenerated from the integration circuit 30. The amplifier 42 amplifiesthe sampled and held detection voltage Vs when necessary. The A/Dconverter 44 converts the amplified detection voltage Vs into a digitalvalue Ds indicating a change in capacitance of each capacitive sensorunit 5.

The controller 50 controls an operation sequence of the transmittercircuit 20 and the receiver circuit 26. In addition, the controller 50controls an operation mode of the transmitter circuit 20, which will bedescribed later.

In the first embodiment, the transmitter circuit 20 is configured toswitch between a first mode and a second mode. In the first mode, thetransmitter circuit 20 sequentially applies the transmission signal S1to the plurality of transmitter electrodes 10 _([1 to M]). In the secondmode, the transmitter circuit 20 virtually classifies the plurality oftransmitter electrodes 10 _([1 to M]) into at least one group andsimultaneously applies the same transmission signal S1 to a plurality oftransmitter electrodes 10 belonging to the same group.

FIGS. 3A and 3B are operation waveform diagrams of the transmittercircuit 20 in the first mode and the second mode, respectively. As shownin FIG. 3A, in the first mode, the plurality of transmitter electrodes10 _([1 to M]) is sequentially scanned and the transmission signal S1 isapplied to a selected transmitter electrode in a time-divisional manner.In the second mode of FIG. 3B, the plurality of transmitter electrodes10 _([1 to M]) belongs to a single group and the common transmissionsignal S1 is applied to all of the transmitter electrodes 10_([1 to M]).

In the second mode, the number of groups of transmitter electrodes maybe one or more. In some embodiments, the number of groups, in otherwords, the number of transmitter electrodes 10 belonging to a singlegroup may be changed.

FIGS. 4A to 4C are operation waveform diagrams of M number of thetransmitter circuit 20 where the number of groups is 1 to 3,respectively. In FIG. 4A, a single group G1 is formed and the sametransmission signal S1 is simultaneously applied to all transmitterelectrodes 10 _([1 to M)] belonging to the group G1. In FIG. 4B, twogroups G1 and G2 are formed and are sequentially scanned. During aperiod of time when the group G1 is selected, the transmission signal S1is applied to the transmitter electrodes 10 _([1 to 6]) belonging to thegroup G1. During a period of time when the group G2 is selected, thetransmission signal S1 is applied to the transmitter electrodes 10_([7 to 12]) belonging to the group G2. FIG. 4C shows a case where threegroups are formed. It is also to be understood that four and six groupsmay be formed without departing from the spirit and scope of the presentdisclosure.

FIGS. 5A to 5C are circuit diagrams showing configurations of thetransmitter circuit 20 of FIG. 2. Each of transmitter circuits 20 a and20 b of FIGS. 5A and 5B, respectively, includes drivers 24 _([1 to M])provided for the respective transmitter electrodes 10 _([1 to M]), asignal generator 22, a demultiplexer 23 and a decoder 25. The signalgenerator 22 generates a periodical signal (clock signal) to be appliedto the transmitter electrodes 10 in each mode. The demultiplexer 23receives the periodical signal from the signal generator 22 anddistributes it to several selected ones of the drivers 24 _([1 to M]).In the first mode for example, the demultiplexer 23 sequentially selectsone of the plurality of drivers 24 _([1 to M]) and outputs theperiodical signal to the selected one of the drivers 24 _([1 to M]).

The demultiplexer 23 of FIG. 5A includes a plurality of selectorsSEL_([1]) to SEL_([M]). If a control signal CNT for an i-th selectorSEL_([i]) is “1”, an output of the selector SEL_([i]) corresponds to theperiodical signal from the signal generator 22, which results in a statewhere the corresponding transmitter electrode 10 _([i]) is selected. Onthe contrary, if the control signal CNT for the i-th selector SEL_([i])is “0”, an output of the selector SEL_([i]) corresponds to zero, whichresults in a state where the corresponding transmitter electrode 10_([i]) is not selected. The decoder 25 generates different controlsignals CNT depending on the mode and the number of groups.

The demultiplexer 23 of FIG. 5B includes logic gates (AND gates) insteadof the selectors SEL of FIG. 5A. If a control signal CNT for an i-th ANDgate AND_([i]) is “1”, an output of the AND gate AND_([i]) correspondsto the periodical signal from the signal generator 22, which results ina state where the corresponding transmitter electrode 10 _([i]) isselected. On the contrary, if the control signal CNT for the i-th ANDgate AND_([i]) is “0”, an output of the AND gate AND_([i]) correspondsto zero, which results in a state where the corresponding transmitterelectrode 10 _([i]) is not selected. The AND gates may be replaced withOR gates, in which case the logic of the control signal may be inverted.

A transmitter circuit 20 c of FIG. 5C includes a plurality of drivers 24_([1 to M]) and a signal generator 22 c. The signal generator 22 coutputs a periodical signal to the plurality of drivers 24 _([1 to M])depending on the mode and the number of groups.

The configuration of the control circuit 100 has been described in theabove. Subsequently, an operation thereof will be described for eachmode.

<First Mode>

In the first mode, the plurality of transmitter electrodes 10_([1 to M]) is sequentially scanned. Accordingly, a spatial resolutionfor a first direction in which the transmitter electrode 10[1 to M] arearranged is maximized so that the electrostatic capacitive sensor 4 canbe used as a typical touch panel sensor.

<Second Mode>

In the second mode, the plurality of transmitter electrodes 10_([1 to M]) is grouped. For example, if all of the transmitterelectrodes 10 _([1 to M]) are grouped in a single group, an apparentarea of the transmitter electrodes 10 becomes substantially M times aslarge as that of the first mode. As a result, sensitivity can be greatlyimproved although the spatial resolution for the first direction may belost. This allows for detection of a detection target such as a finger,a head, a stylus or the like in proximity to the panel and notcontacting the panel.

In this manner, when the control circuit 100 according to thisembodiment is set to the second mode, the electrostatic capacitivesensor 4 can be operated as a proximity sensor.

In addition, by changing the number of groups in the second mode, thatis, the number of transmitter electrodes 10 to be simultaneouslyselected, it is possible to control the spatial resolution and thedetection sensitivity which are in a trade-off relationship.

FIGS. 6A to 6C are views showing usage of the input device 2 in eachmode. In each of FIGS. 6A to 6C, a detectable range RNG of the detectiontarget 6 such as a user's finger is shown. FIG. 6A shows a case of theminimum number of groups in the second mode. In this case, thedetectable range RNG is maximized so that the electrostatic capacitivesensor 4 can be used as a proximity sensor.

FIG. 6B shows a case when the number of groups is increased in thesecond mode. In this case, the detectable range RNG is decreased.Accordingly, a coordinate of the detection target 6 can be detected witha rough precision when it becomes closer to the electrostatic capacitivesensor 4 than in the case shown in FIG. 6A, although the coordinate canbe detected while the detection target 6 does not contact with theelectrostatic capacitive sensor 4. This usage is suitable for detectionof a user's input manipulation at a position distant from the panel,which is called “hovering.”

In addition, in the second mode, the increase in the number of groupshelps to manipulation of the electronic equipment 1 by a gloved user. Agloved condition provides less change in mutual capacitances than anungloved condition. On the other hand, the gloved condition requires nohigh spatial resolution. Accordingly, in this gloved condition, acomfortable input manipulation is enabled by appropriately setting thenumber of groups in the second mode. FIG. 6C shows a case where thenumber of groups is increased and the detectable range RNG is decreasedthan the case shown in FIG. 6B

The following description is given to mode control. The controller 50controls an operation mode of the transmitter circuit 20. When thetransmitter circuit 20 is set to the second mode and the input device 2acts as a proximity sensor, the input device 2 cannot act as a typicaltouch sensor due to a low spatial resolution for the first direction. Inthis case, the controller 50 may switch the operation status of thetransmitter circuit 20 between (i) a first condition where thetransmitter circuit 20 is fixedly set to the first mode and (ii) asecond condition where the transmitter circuit 20 is set to alternatebetween the first mode and the second mode in a time-divisional manner.

FIGS. 7A and 7B are operation waveform diagrams in the first and secondconditions, respectively. In many cases, the input device 2 is notrequired to function as a proximity sensor during user's inputmanipulation by touch. In these cases, by setting the transmittercircuit 20 to the first condition, a touch input coordinate by a user isdetected with the maximum spatial resolution. In FIGS. 7A and 7B, “A”denotes a period of time during which one frame is scanned in the firstmode and “B” denotes a period of time during which one frame is scannedin the second mode. As shown in FIG. 7A, in the first condition, inorder to detect a minute touch input at a high speed, a repetitionperiod Tp is set to be short and a temporal resolution is set to behigh. For example, Tp may be set to 10 ms or so.

On the other hand, if there is no touch input, the transmitter circuit20 is set to the second mode and alternates between the first mode andthe second mode in a time-divisional manner, so that the input device 2can detect touch input while monitoring proximity of the detectiontarget to the panel. i.e., acting as a proximity sensor. This canprovide the same manipulation feeling as the case where a conventionaltouch sensor and an optical proximity sensor are used in combination. Inaddition, as shown in FIG. 7B, a repetition period Tp in the secondcondition may be set to be longer than that in the first condition. Forexample, the repetition period Tp in the second mode may be set to 100ms or so. This can prevent power consumption in the second conditionfrom being increased. When the touch input is detected in the secondcondition, the transmitter circuit 20 immediately makes a transition tothe first condition to detect a subsequent touch input at a high speed.

Second Embodiment

In the first embodiment, the transmitter circuit 20 has been configuredto switch between modes. On the contrary, in the second embodiment, thereceiver circuit 26 is configured to switch between modes for control ofsensitivity. In the following description, portions common to the firstand second embodiments are incorporated by reference and explanation ofwhich is not repeated.

The receiver circuit 26 is configured to switch between a first mode anda second mode. In the first mode, the receiver circuit 26 monitorsreception signals I_(RX[1]) to I_(RX[N]) generated in a plurality ofreceiver electrodes 12 _([1 to N]), respectively, and generates adetection signal Vs for each of the receiver electrodes 12.

In the second mode, the receiver circuit 26 groups the plurality ofreceiver electrodes 12 _([1-N]), connects the receiver electrodes 12belonging to the same group in common, and generates a detection signalfor each group. In addition, the receiver circuit 26 may be configuredto change the number of groups in the second mode. In other words, thenumber of receiver electrodes 12 connected in common may be changed.

The controller 50 may switch the operation status of the receivercircuit 26 between a first condition where the receiver circuit 26 isfixedly set to the first mode and a second condition where the receivercircuit 26 is set to alternate between the first mode and the secondmode in a time-divisional manner. The switching operation is the same asthat in the first embodiment.

FIGS. 8A and 8B are circuit diagrams showing example configurations ofthe receiver circuits 26 of the control circuit 100 according to thesecond embodiment. A receiver circuit 26 a of FIG. 8A includesintegration circuits 30 _([1 to N]) provided for the respective receiverelectrodes 12 _([1 to N]), a plurality of first analog switches SW1_([1 to N]), a plurality of second analog switches SW2 _([1 to N-1]) anda decoder 27 a.

A j-th first analog switch SW1 _([j]) is interposed between acorresponding receiver (RX) terminal RX_([j]) and an input terminal of acorresponding integration circuit 30 _([j]). A j-th second analog switchSW2 _([j]) is interposed between the input terminal of the correspondingintegration circuit 30 _([j]) and an adjacent integration circuit 30_([j+1]). A decoder 27 a controls the analog switches SW1 and SW2depending on the mode. Specifically, in the first mode, all of the firstanalog switches SW1 _([1 to N]) are switched on and all of the secondanalog switches SW2 _([1 to N-1]) are switched off.

In the second mode, one integration circuit 30 is allocated for eachgroup. When an integration circuit 30 _([j]) is allocated to a group,the switches SW1 and SW2 interposed between all receiver electrodes 12and the integration circuit 30 _([j]) are switched on.

In a receiver circuit 26 b of FIG. 8B, the plurality of receiverelectrodes 12 _([1-N]) shares the less number of integration circuits30. The number of integration circuits 30 may be one, two or four. Aj-th third analog switch SW3 _([j]) is interposed between thecorresponding RX terminal RX_([j]) and an input terminal of acorresponding integration circuit 30. A decoder 27 b controls the thirdanalog switches SW3 _([1 to N]).

In the first mode, N number of third analog switches SW3 _([1 to N]) aresequentially switched on. In the second mode, if the number of groups isone, all of the N number of third analog switches SW3 _([1 to N]) areswitched on simultaneously. In the second mode, if the number of groupsis two or more, these groups are processed in a time-divisional manner.During a period of time when a j-th group is processed, the third analogswitches SW3 interposed between the plurality of receiver electrodes 12belonging to the j-th group and the integration circuit 30 belonging tothe j-th group is switched on.

The configuration of the control circuit 100 according to the secondembodiment has been described in the above. The following description isgiven to an operation of the control circuit 100 for each mode.

<First Mode>

In the first mode, reception signals I_(RX[i to N]) generated by theplurality of receiver electrodes 12 _([1 to N]) are individuallyintegrated to generate detection voltages Vs_([1 to N]). Accordingly, aspatial resolution for the second direction in which the receiverelectrodes 12 _([1 to N]) are arranged is maximized so that theelectrostatic capacitive sensor 4 can be used as a typical touch panelsensor.

<Second Mode>

In the second mode, the plurality of receiver electrodes 12 _([1 to N])is grouped. For example, if all of the receiver electrodes 12_([1 to N]) are grouped in a single group, the apparent area of thereceiver electrodes 12 becomes substantially N times as large as that ofthe first mode. As a result, sensitivity can be greatly improvedalthough the spatial resolution for the second direction may be lost.This allows for detection of a detection target such as a finger, ahead, a stylus or the like in proximity to the panel and not contactingthe panel.

In this manner, when the control circuit 100 according to thisembodiment is set to the second mode, the electrostatic capacitivesensor 4 can be operated as a proximity sensor.

In addition, by changing the number of groups in the second mode, thatis, the number of receiver electrodes 12 connected in common, it ispossible to control the spatial resolution and the detection sensitivitywhich are in a trade-off relationship.

Third Embodiment

FIG. 9 is a matrix table showing the mode combinations of a transmittercircuit and a receiver circuit based on the conditions set by thecontroller according to a third embodiment. A third embodiment is acombination of the first and second embodiments, in which thetransmitter circuit 20 and the receiver circuit 26 are independentlyconfigured to switch between the first mode and the second mode.

The controller 50 may switch the operation status of the transmittercircuit 20 and the receiver circuit 26 under a first condition where thetransmitter circuit 20 and the receiver circuit 26 are fixedly set tothe first mode or the transmitter circuit 20 and the receiver circuit 26are fixedly set to the second mode.

The controller 50 may switch the operation status of the transmittercircuit 20 and the receiver circuit 26 under a second condition wherethe transmitter circuit 20 and the receiver circuit 26 are set toalternate between the first mode and the second mode in atime-divisional manner.

When both of the transmitter circuit 20 and the receiver circuit 26 areset to the first mode under the first condition, the resolutions for thefirst and second directions are maximized so that the electrostaticcapacitive sensor 4 can be used as a typical touch panel sensor. Whenthe transmitter circuit 20 and the receiver circuit 26 are set to thefirst mode and the second mode under the second condition, respectively,sensitivity can be improved with a high resolution for the firstdirection. When the transmitter circuit 20 and the receiver circuit 26are set to the second mode and the first mode under the secondcondition, respectively, sensitivity can be improved with a highresolution for the second direction. When both of the transmittercircuit 20 and the receiver circuit 26 are set to the second mode underthe first condition, sensitivity can be further improved.

According to the third embodiment, by controlling a combination of themodes of the transmitter circuit 20 and the receiver circuit 26 throughthe controller 50, it is possible to control the sensitivity and thespatial resolution more flexibly than the first and second embodiments.

The control circuit 100 according to the first to third embodiments hasbeen described in the above. The following description is given to usageof the control circuit 100.

FIG. 10 is a perspective view showing a mobile phone 700 as one exampleof the electronic equipment 1 having the control circuit 100. The mobilephone 700 includes a housing 702, a speaker 704, a microphone 706, aprotective glass 708, manipulation buttons 710, the electrostaticcapacitive sensor 4 and the control circuit 100. The speaker 704 outputsa voice of a called party in calling. The microphone 706 collects voiceof a user of the mobile phone 700 in calling. The electrostaticcapacitive sensor 4 is disposed on the top side of a display panel (notshown), and the surface of the electrostatic capacitive sensor 4 iscovered by the protective glass 708. The manipulation buttons 710 serveas an input device to allow a user to operate the mobile phone 700. Thecontrol circuit 100 is connected with transmitter electrodes 10 and thereceiver electrodes 12 via wires (not shown). In FIG. 10, thetransmitter electrodes 10 extend in parallel to a short side of thehousing 702 (that is, in an x-axis direction) and the receiverelectrodes 12 extend in parallel to a long side thereof (that is, ay-axis direction). This arrangement of the transmitter electrodes 10 andthe receiver electrodes 12 may be interchangeable.

The configuration of the mobile phone 700 has been described in theabove. The mobile phone 700 eliminates a need of a dedicated proximitysensor using a light emitting device or the like, because theelectrostatic capacitive sensor 4 can be operated as both a touch paneland a proximity sensor through mode switching. Accordingly, productioncosts of the mobile phone 700 can be reduced and the housing 702 of themobile phone 700 can be flexibly designed without being restricted by aproximity sensor.

Subsequently, unique characteristics of proximity detection of themobile phone 700 or similar electronic equipment will be described.

<Side Head Proximity Detection>

Although the electrostatic capacitive sensor 4 can be used as aproximity sensor in the input device 2 according to the above describedembodiments, the mobile phone 700 shown in FIG. 10 requires a functionof detecting proximity of the housing 702 to a side head of a user. Inthis case, there is a need to distinguish a condition where a user putsthe housing 702 in proximity to the side head (hereinafter referred toas a “side head proximity condition”) from other conditions such as acondition where a user covers the input device 2 with hands at thevicinity of the surface of the protective glass 708 or a condition wherethe user grips the housing 702. A technique for detecting the side headproximity condition will be described below.

FIG. 11A is a view showing a side head proximity condition and FIG. 11Bis a view showing an output of the electrostatic capacitive sensor 4under the side head proximity condition. As shown in FIG. 11A, in theside head proximity condition during a calling, the speaker 704approaches a user′ ear. Accordingly, as shown in FIG. 11B, a change incapacitance at the vicinity of the speaker 704 increases and a change incapacitance in the side of the microphone 706 decreases.

Thus, when detecting the side head proximity condition, at least one ofthe transmitter circuits 20 and the receiver circuit 26 of the controlcircuit 100 is set to the second mode so that it can have a spatialresolution in the long side direction (y-axis direction) of the housing702. In the example of FIG. 11B, the receiver circuit 26 is set to thesecond mode and all of the receiver electrodes 12 are grouped into thesame group. On the other hand, the transmitter circuit 20 is set to thefirst mode so that it can have a spatial resolution in the y-axisdirection.

If the transmitter electrodes 10 and the receiver electrodes 12 arearranged in reverse, the transmitter circuit 20 and the receiver circuit26 may be set to the second mode and the first mode, respectively.

The controller 50 of the control circuit 100 or the processor 3receiving an output from the control circuit 100 detects the side headproximity condition based on a digital value Ds corresponding to asensor output (also referred to as “sensor output Ds”). Specifically, ifa change in capacitance in the y-axis direction is large in the vicinityof the speaker 704 that approaches the user′ ear when calling and smallin the vicinity of the microphone 706, it is determined that the mobilephone 700 is in the side head proximity condition. This determinationmay be made by comparing the digital value Ds having a spatialresolution in the y-axis direction with a predetermined pattern.

In this manner, when the electrostatic capacitive sensor 4 is operatedas a proximity sensor, the side head proximity condition can be detectedby providing the electrostatic capacitive sensor 4 with a spatialresolution in the long side of the housing 702.

FIGS. 12A to 12C are views for explaining the side head proximitycondition. FIG. 12A shows a state of the mobile phone 700, FIG. 12Bshows a sensor output Ds from a proximity sensor having a spatialresolution in the y-axis direction, and FIG. 12C shows a sensor outputDs from a touch sensor. FIGS. 13A to 13C are views for explaining acondition where a user touches the vicinity of the speaker 704 of theelectrostatic capacitive sensor 4. FIG. 13A shows a state of the mobilephone 700, FIG. 13B shows a sensor output Ds from a proximity sensorhaving a spatial resolution in the y-axis direction, and FIG. 13C showsa sensor output Ds from a touch sensor.

As shown in FIGS. 12B and 13B, there may be some cases where the twoconditions shown in FIGS. 12A and 13A cannot be distinguished with onlya spatial resolution in the y-axis direction. In these cases, as shownin FIG. 13C, the two conditions can be distinguished by operating theelectrostatic capacitive sensor 4 as a touch sensor so that it can havespatial resolutions in both the x-axis and y-axis directions. When theelectrostatic capacitive sensor 4 is operated in the second condition asshown in FIG. 7B, the electrostatic capacitive sensor 4 can distinguishthe condition of FIG. 12A and the condition of FIG. 13A because theelectrostatic capacitive sensor unit 4 acts as a proximity sensor havinga spatial resolution in the y-axis direction and as a touch sensorhaving spatial resolutions in the x-axis and y-axis directions.

<Grip Detection>

In electronic equipment such as the mobile phone 700, there are somecases in which a condition where a user grips a housing is required tobe detected. FIGS. 14A and 14B show that an input device 2 according tothe embodiments can be also used for a grip sensor. FIG. 14A is a viewshowing a grip condition and FIG. 14B is a view showing an output of theelectrostatic capacitive sensor 4 under the grip condition. In the gripcondition as shown in FIG. 14A, a change in capacitance of the receiverelectrodes 12 at one end of a display to which a user′ thumb approachesand of the receiver electrodes 12 at the other end of the display towhich the other fingers approach increases, while a change incapacitance of the receiver electrodes 12 disposed in the center of thedisplay decreases.

Thus, when the grip condition is detected, at least one of thetransmitter circuit 20 and the receiver circuit 26 of the controlcircuit 100 is set to the second mode so that it can have a spatialresolution in the short side direction (x-axis direction) of the housing702. In the example of FIG. 14B, the transmitter circuit 20 is set tothe second mode and all of the transmitter electrodes 10 are groupedinto the same group. On the other hand, the receiver circuit 26 is setto the first mode so that it can have a spatial resolution in the x-axisdirection.

If the transmitter electrodes 10 and the receiver electrodes 12 arearranged in reverse, the transmitter circuit 20 and the receiver circuit26 may be set to the first mode and the second mode, respectively.

The controller 50 of the control circuit 100 or the processor 3receiving an output from the control circuit 100 detects the gripcondition based on the digital value Ds corresponding to the sensoroutput. Specifically, if a change in capacitance in both ends at thevicinity of the lower and the upper limit of x coordinates is large, itis determined that the mobile phone 700 is in the grip condition. Thisdetermination may be made by comparing the digital value Ds having aspatial resolution in the x-axis direction with a predetermined pattern.

In this manner, when the electrostatic capacitive sensor 4 is operatedas a proximity sensor, the grip condition can be detected by providingthe electrostatic capacitive sensor 4 with a spatial resolution in theshort side of the housing 702.

In the above, the present disclosure has been described by way ofspecific embodiments. The disclosed embodiments are merely examples andit is to be understood by those skilled in the art that combinations ofelements and processes of the embodiments can be modified in variousways and such modification falls within the scope of the presentdisclosure. The following description is given to such modification.

Although an operation of setting the transmitter circuit 20 or thereceiver circuit 26 to the second mode when the electrostatic capacitivesensor 4 is used as a proximity sensor has been illustrated in the aboveembodiments, the present disclosure is not limited thereto. For example,when the electrostatic capacitive sensor 4 is used as a touch sensor,the transmitter circuit 20 or the receiver circuit 26 may be set to thesecond mode and a plurality (for example, two) of the transmittercircuits 20 or the receiver circuits 26 may be allocated for each group.In this case, the amplitude of the reception signal I_(RX) is increased,which may result in reduction of the number of integrations performed bythe integration circuit 30 and power consumption in the integrationcircuit 30. In this case, since a spatial resolution in the touch sensoris decreased, such setting may be performed under a condition where ahigh spatial resolution is not required (for example, in a case where anicon on a home screen of the mobile phone 700 is selected).

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosures. Indeed, the novel methods and apparatusesdescribed herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe embodiments described herein may be made without departing from thespirit of the disclosures. The accompanying claims and their equivalentsare intended to cover such forms or modifications as would fall withinthe scope and spirit of the disclosures.

What is claimed is:
 1. A control circuit of an electrostatic capacitivesensor including a plurality of transmitter electrodes disposed inparallel in a first direction and a plurality of receiver electrodesdisposed in parallel in a second direction, and spaced apart from theplurality of transmitter electrodes by specific intervals, the controlcircuit comprising: a transmitter circuit configured to apply aperiodical transmission signal to each of the plurality of transmitterelectrodes; a receiver circuit configured to generate, based on areception signal generated in each of the plurality of receiverelectrodes in response to the transmission signal, a detection signalindicating a change in electrostatic capacitance formed at each ofintersections of the plurality of transmitter electrodes and theplurality of receiver electrodes; and a controller configured to controloperation modes of the transmitter circuit and the receiver circuit,wherein the transmitter circuit is configured to switch between a firstmode, where the transmission signal is sequentially applied to theplurality of transmitter electrodes, and a second mode, where theplurality of transmitter electrodes are grouped into one or more groupsand the transmission signal is simultaneously applied to transmitterelectrodes belonging to the same group, wherein the receiver circuit isconfigured to switch between a first mode, where the reception signalgenerated in each of the plurality of receiver electrodes issequentially monitored to generate the detection signal for each of thereceiver electrodes, and a second mode, where the plurality of receiverelectrodes are grouped into one or more groups and receiver electrodesbelonging to the same group are connected in common to generate thedetection signal for each group, and wherein the controller switchesbetween a first condition, where the transmitter circuit and thereceiver circuit are fixedly set to the first mode, and a secondcondition, where the transmitter circuit and the receiver circuit areset to alternate between the first mode and the second mode in atime-divisional manner.
 2. The control circuit of claim 1, wherein thereceiver circuit is configured such that a number of the one or moregroups can be changed in the second mode.